This red-leafed Italian chicory is most often used as a salad green. There are several varieties of radicchio, but the two most widely available in the United States are Verona and Treviso. The radicchio di Verona has burgundy-red leaves with white ribs. It grows in a small, loose head similar to butterhead lettuce. The leaves of radicchio di Treviso (commonly referred to simply as Treviso) are narrow and pointed and form tighter, more tapered heads. They also have white ribs but can range in color from pink to dark red. Other radicchio varieties have variegated or speckled leaves in beautiful shades of pink, red and green. All radicchios have tender but firm leaves with a slightly bitter flavor. Radicchio is available year-round, with a peak season from midwinter to early spring. Choose heads that have crisp, full-colored leaves with no sign of browning. Store in a plastic bag in the refrigerator for up to a week. Besides being used in salads, radicchio may also be cooked by grilling, sautéing or baking.